There was a discussion on the Amherst Town Meeting mailing list a while ago about paper versus plastic versus cloth grocery bags, which poked my "skeptical" and "libertarian" buttons.
"Skeptical" because I think much of the debate over paper versus plastic is driven by the "natural must be better" fallacy. Plastic comes from nasty, icky oil, and so must be worse for the environment than paper, which comes from beautiful, majestic trees. Cutting down beautiful, majestic trees to make paper is evil, too, of course, so we should all re-use organic hemp shopping bags.
"Libertarian" because the idea of Town Meeting deciding what the best way of bringing my groceries home just rubs me the wrong way; we'll all have different opinions on how much we value saving the environment, convenience, hygiene, cost, and signaling our environmental bona-fides by schlepping around filthy, tattered, disease-ridden reusable bags. (I'm skeptical of the idea that reusable bags are dangerous due to germs, but I respect that some people are genuinely worried about that)
So I was please to run across this thorough, data-driven study of plastic versus paper versus cloth bags on the environment:
As far as I can tell, it's not a fluff piece sponsored by the Plastic Bag Council of Wales-- the study was sponsored by the Environment Agency, "a British non-departmental public body of the Department for Environment, Food and Rural Affairs and an Assembly Government Sponsored Body of the Welsh Government that serves England and Wales."
Looks like if you use your cotton bags more than 130 times, and you just throw out your plastic shopping bags, then cloth is better than plastic. I use ours probably twice a week, and they seem to last 3 or 4 years (about 300 or 400 re-uses), so definitely in the better-for-the-environment category.
So policy-wise, a disposable-bag-tax to encourage use of re-usable bags would be the smart thing to do.
Unless that means more people drive a little farther to Stop and Shop in Hadley instead of Big Y in Amherst, of course. I'd bet gasoline usage getting to the store is hundreds of times more damaging to the environment than what kind of bag you use. Charging 25cents for parking at the grocery store would probably be even better public policy.
PS: I generally don't like collecting things, but make an exception for reusable bags-- we've been collecting them from trips overseas. The little cloth bag we got from our stay in Yungaburra is my favorite, although the big re-usable plastic bag from Paris is probably the most functional. Travelling by airplane is absolutely terrible for the environment, though...